The 4th and 6th Provisional Mixed Colonial Infantry Regiments (Regiments Mixtes de Marche d'Infanterie Coloniale) were formed in the winter of 1915 by combining battalions of Senegalese Rifles (Tirailleurs Senegalais) with battalions of European colonial infantry. They were assigned to the 2nd Mixte Colonial Infantry Brigade (2e Brigade Mixte d'Infanterie Coloniale) of the 1st Infantry Division of the Dardanelles Expeditionary Corps (1e Division d'Infanterie du CED) and, as might be expected, took part in the Gallipoli campaign. When that ended, they joined the polyglot expeditionary force at Salonika.
In the course of the first two years of the war, the names of the regiments changed, first to the 4th and 6th Mixed Colonial Infantry Regiments and then to the 54th and 56th Colonial Infantry Regiments. (The final transformation may have involved the replacement of Senegalese battalions with European ones.)
An overview of the division to which these regiments were assigned can be found onhttp://toaw.free.fr/...C-pp992-993.jpg